The present invention relates generally to storage of foodstuffs and more particularly to a system or apparatus for supplying, adjusting and maintaining an aseptic atmosphere and pressure in a storage tank with a foodstuff as contents therein.
In the field of food processing, in which agricultural products are process into foods, the products produced on a farm are not immediately processed into their final form of processed foods since they have season-dependent characteristics and are harvested in large quantities at a time. The agricultural products are partially processed and are stored in storage tanks or containers in the form of half-processed products or primarily-processed products and are then processed into final food products as they are withdrawn from the storage container.
An example is tomatoes which have seasonal characteristics and are harvested in large quantities at a time and are processed into final food products such as tomato sauce, tomato ketchup or the like, before final processing they are temporarily stored in the form of a puree or paste, i.e. a primarily-processed product. These primarily-processed food products are then processed into final food products, such as tomato, sauce, tomato ketchup or the like as the primary processed product is withdrawn from the temporary storage container.
A most important thing in the series of steps of production of processed foods is to store the primarily-processed product in a perfectly sterilized state. Storing primarily-processed food products in a large storage tank is the most effective and most used method at present. However, when the primarily-processed food products are stored in a large storage tank, the temperature thereof must be kept as low as possible taking into account the possibility of deterioration and viscosity resistance thereof. In addition, much attention must be paid to the prevention of microbiological contamination of these primarily-processed food products. The contamination of supply and discharge pipes connected to a large storage tank storing the primarily-processed food products, contamination of a disc for restricting the supply and discharge flows of the primarily-processed product, contamination of the tank itself and its attachments or accessories, and the entry or invasion of contaminating microorganisms, must be strictly prohibited, even if such contamination is extremely small.
Various methods of and apparatus for storing primarily-processed food products in an aseptic manner have been disclosed in, for example, U.S. Pat. Nos. 3,871,824, 3,918,678, 3,918,942, 3,951,184 and 3,998,589 granted to Rechtsteiner.
For safety storing primarily-processed food products in an aseptic manner in an aseptic storage tank, it is necessary to maintain a positive pressure of aseptic gas in the storage tank. At the same time, it is necessary to provide an anti-explosion safety device to avoid an explosion resulting from an extraordinarily high internal pressure which may result from accidental rot of the primarily-processed food product in the tank.
According to the prior art, the aseptic gas is introduced into the tank through a microbiological filter attached to the tank, so as to maintain a positive pressure in the tank. A safety or relief valve for anti-explosion purposes is attached to the tank separately from the filter.
Taking into account that even slightly microbiological contamination can finally grow to deteriorate the whole of the contents of a storage system the number of parts, which may constitute causes of contamination, must be reduced as great as extent as possible. The known arrangements in which a microbiological filter and a safety valve are installed separately in the system increases the chances of contamination.
Particularly, specific attention must be paid in the known systems to the sterilization and cleaning of the safety valve. The parts around the safety valve directly attached to the tank require a supply of sterilizer and cleaning agent.
It is of great importance to ensure microbiological cleanliness, in order to store primarily-processed products for a long period of time in an aseptic state.